With the success of HIV prevention and treatment efforts in the United States (US), disparities in HIV incidence and prevalence have grown. HIV is now considered an epidemic of the socially marginalized and disenfranchised, with cases concentrated in racial and sexual minorities in impoverished neighborhoods, particularly African Americans and men who have sex with men (MSM). The rates of substance use, like stimulant use, are high within these groups and further increase engagement in risky sexual behaviors. Neurobehavioral researchers are elucidating brain regions involved in risky decision making, and factors like drug use, socioeconomic disadvantage, and social marginalization have been linked to alterations in these regions. Understanding how substance use and social inequalities influence decision making facilitates our ability to tailor HIV prevention interventions to high-rik groups; however socially disadvantaged substance users are rarely included in neuroimaging research, partly due to a deficiency in recruitment strategies. The proposed project integrates training and research designed to develop the applicant's expertise in functional magnetic resonance imaging (fMRI) design and analysis with disadvantaged stimulant users. The proposed project will build on the applicant's strong foundation in clinical psychology, by providing mentored training in (1) neurobehavioral aspects of substance use and HIV/AIDS, (2) fMRI design, analysis, and interpretation, (3) respondent-driven sampling (RDS) and other strategies for recruiting disadvantaged substance users for neuroimaging research. The training plan includes coursework, participation in seminars, directed readings, mentored research, attendance at national conferences, and mentored grant writing. The proposed research will examine the main and interaction effects of socioeconomic status and cocaine use on risky decision making and associated neural activation using data collected from NIDA-funded fMRI research overseen by the applicant's mentor. It is hypothesized that cocaine use and low SES will be associated with riskier decision making and decreased neural activation during an experimental loss aversion task. Additionally, RDS will be used to recruit 100 MSM cocaine users to determine its feasibility and to identify factors associated with willingness to participae in fMRI research. This research will inform patient-oriented research aimed at reducing HIV disparities among disadvantaged substance users. At the culmination of this fellowship, the applicant will have specialized expertise in an area of critical need and will be prepared to begin a program of patient- oriented research in the fields of neuroAIDS and drug abuse.